King Richard was French and the legend of Robin usually portrays him as one of Richard's Knights/Earls that has been outlawed. If he existed at all,I doubt if he would have spoken with a present day accent of any sort. We will never know what any accent was like 800 years ago! Accents change and develop in relatively short periods of time, lookm at the USA and Australia as examples. What is important is good acting and clear speech, after all the purpose of the film is entertainment. I am always skeptical of films that say things such as "The Untold Story" "The Truth Behind The Fiction" The Arthur film a few years back was another example of such tripe.

P.S. Where's my plectrum?